Method and apparatus for handover in communication system

ABSTRACT

A method for a serving base station to determine a handover time in a communication system is provided. The method includes determining whether to set up dual connectivity (DC) with respect to a terminal with a target base station that transmits the beacon if it is recognized that the terminal receives a beacon including a plurality of pieces of service coverage area information, and determining whether to execute a handover to the target base station based on a measurement report of the terminal, which is received after the DC is set up if the DC is set up.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 U.S.C. §119(a) of a Koreanpatent application filed on Jun. 5, 2013 in the Korean IntellectualProperty Office and assigned Serial number 10-2013-0064657, the entiredisclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a handover method and apparatus in acommunication system.

BACKGROUND

In a related-art communication system, when a handover caused bymovement of a mobile station (MS) is executed, a target base station(BS) to which the MS is to be handed over and a handover time aredetermined based on a channel environment-related report associated witha neighboring base station that a serving BS receives from the MS.

However, the connection between the MS and the serving BS may bedisconnected in a radio shadow zone, before the serving BS transmits ahandover command to the MS. In this instance, handover operations of theserving BS may not be smoothly executed. For example, in the case of amillimeter wave system introduced for satisfying the increasing demandof radio data traffic, a degree of a decrease in signal strength issignificantly higher than other systems when the signal passes throughan obstacle. Accordingly, when an event in which the MS passes throughan obstacle, enters inside, or goes into a basement occurs, theconnection with the MS may be disconnected before the serving BSdetermines the target BS to which the MS is to be handed over and anappropriate handover time. In this instance, the MS faces a radio linkfailure (RLF) situation before recognizing that the MS is out of aservice coverage area of the serving BS due to the movement of the MSand should be handed over. When the connection between the MS and a newBS is set up through a related-art RLF overcome process, the serviceinterruption occurring during the RLF overcome process takes longer andthe continuity of the service may not be obtained even though the MSattempts to reopen the service that has been provided from the existingserving BS.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method and apparatus for determining ahandover time in a communication system.

Another aspect of the present disclosure is to provide a method ofdetermining a handover time through reporting of information andcommunication between a serving base station (BS) and the target BS whena mobile station (MS) is located in a radio shadow zone in acommunication system including a plurality of service coverage areas.

In accordance with an aspect of the present disclosure, a handovermethod of a serving base station in a communication system is provided.The method includes if it is recognized that a terminal receives abeacon including a plurality of pieces of service coverage areainformation, determining setup of dual connectivity (DC) with respect tothe terminal with a target base station that transmits the beacon, and,if the DC is set up, determining whether to execute a handover to thetarget base station based on a measurement report of the terminal whichis received after the DC is set up.

In accordance with another aspect of the present disclosure, a handovermethod of a target base station in a communication system is provided.The method includes in a state where the target base station thatsupports a plurality of service coverage areas has dual DC set with aserving base station of a terminal and the terminal, receiving from theterminal, a measurement report associated with a beacon of the targetbase station, and, determining whether to execute a handover of theterminal based on the measurement report.

In accordance with another aspect of the present disclosure, a handovermethod of a terminal in a communication system is provided. The methodincludes if a beacon transmitted by a target base station that providesa plurality of service coverage areas is received, transmittingbeacon-related information to a serving base station, receiving, fromthe serving base station, information for DC with the target basestation, and, transmitting a measurement report corresponding to acoming period to the serving base station and the target base stationbased on the information for the DC.

In accordance with another aspect of the present disclosure, a servingbase station that executes a handover in a communication system isprovided. The serving base station includes a controller configured todetermine setup of DC with a target base station that transmits thebeacon to the terminal if it is recognized that a terminal receives abeacon including a plurality of pieces of service coverage areainformation, and if the DC is set up, to determines whether to execute ahandover to the target base station based on a measurement report of theterminal which is received after the DC is set up.

In accordance with another aspect of the present disclosure, a targetbase station that executes a handover in a communication system isprovided. The target base station includes a receiving unit configuredto receive, from a terminal, a measurement report associated with abeacon of the target base station in a state where the target basestation that supports a plurality of service coverage areas has DC setwith a serving base station of the terminal and the terminal, and, acontroller configured to determine whether to execute a handover of theterminal based on the measurement report.

In accordance with another aspect of the present disclosure, a terminalthat executes a handover in a communication system is provided. Theterminal includes a controller configured to control a transceiving unitto transmit beacon-related information to a serving base station if theterminal receives a beacon transmitted by a target base station thatprovides a plurality of service coverage areas, to receive, from theserving base station, information for DC with the target base station,and to transmit a measurement report corresponding to a coming period,to the serving base station and the target base station, based on theinformation for the DC.

According to the present disclosure, if a MS receives a beacon of aservice coverage area that is capable of supporting a quality of service(QoS) used by the MS, DC with a target BS that transmits the beacon isset up, and a handover time is adjusted by adjusting a period of ameasurement report based on a signal strength of the beacon associatedwith the target BS. Therefore, the present disclosure may provide thecontinuity of a service of a terminal and may support QoS even if signalstrength decreases significantly due to an obstacle based on acharacteristic of a high frequency band, and even if the terminal islocated in a radio shadow zone of other different frequency bands.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram illustrating an example of a movement of a MobileStation (MS) in a communication system including a plurality of servicecoverage areas according to an embodiment of the present disclosure;

FIGS. 2A and 2B are examples of a flowchart of operations of a servingBase Station (BS) according to an embodiment of the present disclosure;

FIG. 3 is an example of a flowchart of operations of a target BSaccording to an embodiment of the present disclosure;

FIG. 4 is an example of a signal flow diagram of case 1 of FIGS. 2A and2B according to an embodiment of the present disclosure;

FIGS. 5A and 5B are examples of a signal flow diagram of case 2 of FIGS.2A and 2B according to an embodiment of the present disclosure;

FIG. 6 is another example of a signal flow diagram of case 2 of FIGS. 2Aand 2B according to an embodiment of the present disclosure;

FIG. 7 is an example of a block diagram of a serving BS and a target BSaccording to an embodiment of the present disclosure;

FIGS. 8A and 8B are examples of a signal flow diagram of DualConnectivity (DC) according to an embodiment of the present disclosure;

FIG. 9 is an example of a flowchart of operations of an MS according toan embodiment of the present disclosure; and

FIG. 10 is an example of a block diagram of an MS according to anembodiment of the present disclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, description of well-known functions orconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

FIG. 1 is a diagram illustrating an example of a movement of a mobilestation (MS) in a communication system including a plurality of servicecoverage areas according to an embodiment of the present disclosure.

Referring to FIG. 1, for example, when the case of a millimeter wavecommunication system is assumed, a small base station (BS) 110 may beinstalled to reduce service interruption caused by a radio shadow zone,which is the result of the loss of signal strength due to an obstacle,or the like. Accordingly, the communication system includes a servingbase station (BS) 100 and the small BS 110 and thus, each BS transmits abeacon having a different service coverage area. For example, theserving BS 100 may correspond to a 3^(rd) generation partnership project(3GPP) pico base station (BS), a millimeter wave pico BS, and the like.The small BS 110 may correspond to a wireless local area network (LAN)or the like that is installed to be integrated into the serving BS 100.In this instance, a beacon transmitted by the small BS 110 may include afield that indicates the small BS 110 is a BS integrated into theserving BS 100. The serving BS 100 may receive a result of reception ofthe beacon from an MS 105, and may use the result in a process ofdetermining a handover.

Here, as an example, it is illustrated that the MS 105 moves to aservice coverage area of the small BS 110. The service coverage area ofthe small BS 110 may be distinguished, based on, for example, a building117, as an internal service coverage area 115 of an internal area of thebuilding 117 and an external service coverage area 120 of an externalarea of the building 117. Accordingly, the small BS 110 broadcastsdifferent beacons respectively corresponding to the internal servicecoverage area 115 and the external service coverage area 120.

As described above, a communication system including a plurality ofservice coverage areas according to an embodiment of the presentdisclosure may include, for example, the case that is based on differentradio access systems (e.g., radio access technology (RAT)) such as theservice BS 100 and the small BS 110 of FIG. 1. In this example,switching an RAT is performed when the MS 105 is handed over between theserving BS 100 and the small BS 110. As another example, the case inwhich a single communication system operates a plurality of frequencybands and a beacon associated with each frequency band is transmittedmay be included. In this example, determination associated with thechange of a frequency band may be performed based on resource allocationwhen an MS is handed over between service coverage areas of thefrequency bands.

FIGS. 2A and 2B are examples of a flowchart of operations of a servingBS according to an embodiment of the present disclosure. Here, for easeof description, the operations of the serving BS 100 will be describedbased on the communication system of FIG. 1.

Referring to FIGS. 2A and 2B, the serving BS 100 transmits, to the MS105, a neighboring BS signal measurement report request in operation202. When the ‘neighboring BS signal measurement report’ is receivedfrom the MS 105 in operation 204, the serving BS 100 determines whethera target signal of the measurement report corresponds to a beacon of aBS having a plurality of service coverage areas. When the determinationshows that it is different from the beacon of the BS having a pluralityof service coverage areas, the serving BS waits until a correspondingbeacon is received. The determination may be recognized by determiningwhether a field indicating that a BS, which transmits the beacon is a BSintegrated with another BS, exists in the received beacon.

When the determination shows that the field exists and the receivedbeacon corresponds to the beacon of a neighboring BS having a pluralityof service coverage areas, the serving BS proceeds with operation 206.In operation 206, the serving BS 100 determines whether a handovercondition is satisfied based on the measurement report. Here, thehandover condition is set to be the case in which the service coveragearea of the received beacon provides a service with a quality of service(QoS) used by the MS. When the determination shows that the service withthe QoS used by the MS is provided to the MS in a service coverage areacorresponding to the currently received beacon, it is determined thatthe beacon satisfies the handover condition, and the serving BS 100proceeds with case 1 and executes a handover. However, when it isdetermined that the service with the QoS used by the MS is not providedin the service coverage area corresponding to the currently receivedbeacon, the serving BS 100 proceeds with case 2 and determines whetherto set up a dual connectivity (DC).

Hereinafter, case 1 and case 2 according to an embodiment of the presentdisclosure will be described in detail with reference to the signal flowdiagrams of FIGS. 4, 5A, and 5B. First, in case 1, the serving BSdetermines whether a reception strength of a beacon of a neighboring BSis greater than or equal to a handover reference threshold value inoperation 207. When the reception strength is less than the handoverreference threshold value, the serving BS returns to operation 204 andwaits until a beacon of another neighboring BS is received. Here, thehandover reference threshold value may be defined to be a minimumthreshold value of a signal strength for providing a service to the MS.When the received beacon is greater than or equal to the handoverreference threshold value in operation 207, the serving BS 100 executesa handover in operation 208.

When the determination made in operation 206 shows that the receivedbeacon does not satisfy the handover condition, the serving BS 100determines that the service of the QoS used by the MS may be providedthrough another service coverage area of the serving BS, and proceedswith operation 210.

In operation 210, the serving BS 100 sets up dual connectivity (DC) withthe neighboring BS, based on a signal strength associated with a beaconof the neighboring BS. In the present disclosure, the DC is defined tobe the state in which the MS 105 sets up connection with both theserving BS 100 and a target BS for a handover, and is capable ofreceiving a control signal through both the BSs and is capable oftransmitting a report in a determined format to both the BSs. As anexample, it is assumed that the serving BS 100 recognizes that the MShas received a beacon of the neighboring BS, that is, a wireless LANbeacon of the small BS 100, through a relatively low frequency band,while having received a service with a high data rate in a frequencyband having dozens of GHz, and the beacon is transmitted from the smallBS 110, which is a wireless LAN BS integrated with the serving BS 100which is a millimeter wave BS. In this instance, the serving BS 100determines to set up DC of the MS 105, and communicates informationregarding the DC with the neighboring BS, that is, the target BS, andthe MS 105. An example of the information communicated may include thecase of applying a time division scheme and distinguishing a timesection for communication between the target BS and the MS and a timesection for communication between the serving BS and the MS.

According to an embodiment of the present disclosure, the MS for whichDC is set up may receive data service through only the serving BS andmay transmit, to the target BS, a measurement report corresponding tothe communicated information or the format in a corresponding timesection, for the QoS used by the MS. In this example, to the measurementreport that the MS transmits to the target BS, a simple format may beapplied, in comparison to a neighboring BS search report. In particular,information indicating whether a beacon of a service coverage area thatsupports a QoS used by the MS is detected, information indicatingwhether a signal strength of the beacon is greater than or equal to apredetermined threshold value when the beacon is detected, informationindicating whether a signal of the serving BS is received well, and thelike may be included.

In operation 212, the serving BS 100 determines whether a measurementreport is received from the MS 105 for which DC is set up atpredetermined periods. When the determination shows that the measurementreport is not received, the serving BS 100 proceeds with operation A andwaits for the reception of the measurement report. Here, operation A isdefined to be the state in which the DC of the MS 105 is set up.

When the determination shows that the measurement report is receivedfrom the MS 105 for which the DC is set up, the serving BS 100determines, for example, whether the QoS used by the MS 105 is supportedbased on the measurement report, and whether the handover condition issatisfied based on the signal strength of the beacon, in operation 214.In particular, when the serving BS 100 determines, based on themeasurement report, that the beacon that the MS 105 receives may supportthe QoS used by the MS 105 and the signal strength of the beacon isgreater than or equal to the handover reference threshold value, theserving BS 100 determines that the handover condition is satisfied inoperation 214. When the determination shows that the handover conditionis satisfied in operation 214, the serving BS 100 determines aneighboring BS that transmits the QoS supportable beacon to be thetarget BS, and executes a handover in operation 216. In operation 218,the serving BS 100 removes the DC of the MS 105. Here, the handoverreference threshold value is defined to be a minimum threshold value ofa signal strength for providing a service to an MS.

When the determination made in operation 214 shows that the beacon isreceived, but a beacon corresponding to a service coverage area thatprovides the QoS used by the MS is not received, the serving BS 100proceeds with operation 220. In operation 220, the serving BS 100determines whether the signal strength of the beacon is greater than orequal to a first threshold value. The first threshold value is definedto be a threshold value of a signal strength set for determining whetherentry of the MS 105 into the service coverage area of the neighboring BSthat transmits the beacon is close. When the determination shows thatthe signal strength of the beacon is greater than or equal to the firstthreshold value, the serving BS 100 determines that the entry of the MS105 into the service coverage area of the neighboring BS that transmitsthe beacon is close, and proceeds with operation 222. In operation 222,the serving BS 100 sets the current length of a period of a measurementreport of the MS 105 to a minimum value. In operation 224, the servingBS 100 copies and transmits real-time data for data service to theneighboring BS, and returns to operation A.

When the determination made in operation 220 shows that the signalstrength of the current beacon received in the current period is lessthan the first threshold value, the serving BS 100 determines whetherthe signal strength of the current beacon is at least a predeterminedoffset greater than the signal strength of a previous beacon received ina previous period, in operation 226. When the determination shows thatthe signal strength of the current beacon is at least the offset greaterthan the signal strength of the previous beacon, the serving BS 100determines that the entry of the MS 105 into the service coverage areaof the neighboring BS that transmits the current beacon is close, andproceeds with operation 228. In operation 228, the serving BS 100decreases the current length of the period of measurement report of theMS 105 by a predetermined unit. In this instance, the decreased currentlength may be set to a value greater than the minimum value.

When the determination made in operation 226 shows that the signalstrength of the current beacon is not at least the offset greater thanthe signal strength of the previous beacon, the serving BS 100 proceedswith operation 230. In operation 230, the serving BS 100 determineswhether the signal strength of the current beacon is at least the offsetless than the signal strength of the previous beacon. When thedetermination shows that the signal strength of the current beacon is atleast the offset less than the signal strength of the previous beacon,the serving BS 100 increases the current length of the period ofmeasurement report of the MS by the predetermined unit in operation 232.Therefore, when the MS 105 detects a beacon that is capable ofsupporting a QoS, the serving BS 100 according to an embodiment of thepresent disclosure may execute a control for prompt report of the same.

When the determination made in operation 230 shows that the signalstrength of the current beacon is not at least the offset less than thesignal strength of the previous beacon, the serving BS 100 determineswhether the signal strength of the current beacon is less than a secondthreshold value in operation 234. The second threshold value may bedefined to be a signal strength for determining a minimum possibility ofa handover of the MS 105 to the neighboring BS that transmits thecurrent beacon. When the determination shows that the signal strength ofthe current beacon is greater than or equal to the second thresholdvalue, the serving BS 100 returns to operation A. When the signalstrength of the current beacon is less than the second threshold value,the serving BS 100 determines that the possibility of the handover ofthe MS 105 to the neighboring BS that transmits the current beacon iszero, returns to operation 218, and removes the DC of the MS 105.Therefore, the MS that receives a signal strength that is greater thanor equal to the first threshold value, and less than the secondthreshold value may adjust the current length of the period of ameasurement report through the above described processes.

FIG. 3 is a flowchart of operations of a target BS according to anembodiment of the present disclosure. For ease of description, it isassumed that a target BS is the small BS 110 of FIG. 1 based on thecommunication system of FIG. 1.

Referring to FIG. 3, it is assumed that the target BS 110 maintainsoperation A which is the state in which the DC is set up with respect toan MS, together with a serving BS. In operation 302, the target BS 110determines whether a measurement report is received from the MS withwhich the target BS 110 sets up the DC, at predetermined periods. Here,as described in FIGS. 2A and 2B, it is assumed that the format that iscommunicated when the serving BS 100 sets up the DC of the MS is appliedto the measurement report. When the determination shows that themeasurement report is not received, the serving BS 100 proceeds withoperation A and waits for reception of the measurement report.

When the determination shows that the measurement report is receivedfrom the MS for which DC is set up, the target BS 110 determines, forexample, whether a handover condition is satisfied based on themeasurement report in operation 304. In particular, the handovercondition in the embodiment of FIG. 3 may be set to be the case in whichsignal strength information of a beacon that the MS receives is greaterthan or equal to a handover reference threshold value, and the QoS usedby the MS is supported. Here, the handover reference threshold value isdefined to be a minimum threshold value of a signal strength forproviding a service to an MS.

When the determination shows that the handover condition is satisfiedbased on the measurement report, the target BS 110 hands over the MS toitself in operation 306, and the target BS 110 removes the DC of the MSin operation 308. In this example, the removal of the DC of the MS maybe executed when the target BS 110 transmits a signal indicating theremoval of the DC to the serving BS 100.

When the determination made in operation 304 shows that the handovercondition is not satisfied based on the measurement report, the targetBS 110 proceeds with operation 310. In operation 310, the target BS 110determines whether the signal strength of the beacon is greater than orequal to a first threshold value. The first threshold value is definedto be identical to the first threshold value of FIGS. 2A and 2B andthus, a detailed description thereof will be omitted to avoid duplicatedescriptions. When the determination shows that the signal strength ofthe beacon is greater than or equal to the first threshold value, thetarget BS determines that entry of the MS into the service coverage areaof the target BS is close. Therefore, the target BS 110 sets the currentlength of a period of a measurement report of the MS to a minimum valuein operation 312, and thereafter enters operation A. Therefore, when abeacon that is capable of supporting the QoS used by the MS is receivedand the signal strength of the beacon is greater than or equal to thethreshold value, or when a signal from the serving BS is not received,the target BS 110 immediately enters into the state of executing ahandover. Subsequently, the target BS 110 removes the DC with respect tothe MS, and transmits a signal associated with the same to the servingBS 100.

When the determination made in operation 310 shows that the signalstrength of the current beacon received in the current period is lessthan the first threshold value, the target BS 110 determines whether thesignal strength of the current beacon is at least a predetermined offsetgreater than the signal strength of a previous beacon received in aprevious period, in operation 314. When the determination shows that thesignal strength of the current beacon is at least the offset greaterthan the signal strength of the previous beacon, the target BS 110determines that entry of the MS into the service coverage area of itselfis close, and proceeds with operation 316. In operation 316, the targetBS 110 decreases the current length of the period of the measurementreport of the MS 105 by a predetermined unit. In this instance, thedecreased current length may be set to a value greater than the minimumvalue.

When the determination made in operation 314 shows that the signalstrength of the current beacon is not at least the offset greater thanthe signal strength of the previous beacon, the target BS 110 determineswhether the signal strength of the current beacon is at least offsetless than the signal strength of the previous beacon in operation 318.When the determination shows that the signal strength of the currentbeacon is at least the offset less than the signal strength of theprevious beacon, the target BS 110 increases the current length of theperiod of the measurement report of the MS by the predetermined unit inoperation 320. Therefore, when the MS detects a beacon that is capableof supporting the QoS used by the MS, the target BS 110 executes acontrol for prompt report of the same.

When the determination made in operation 318 shows that the signalstrength of the current beacon is not at least the offset less than thesignal strength of the previous beacon, the target BS 110 determineswhether the signal strength of the current beacon is less than a secondthreshold value in operation 322. The second threshold value is definedto be identical to the second threshold value of FIGS. 2A and 2B andthus, detailed descriptions thereof will be omitted to avoid duplicatedescriptions.

When the determination shows that the signal strength of the currentbeacon is greater than or equal to the second threshold value, theserving BS returns to operation A. When the signal strength of thecurrent beacon is less than the second threshold value, the serving BSdetermines that the possibility of the handover of the MS to theneighboring BS that transmits the current beacon is zero, returns tooperation 308, and removes the DC of the MS. Therefore, the MS thatreceives a signal strength that is greater than or equal to the firstthreshold value, and less than the second threshold value, may adjustthe current length of the period for the measurement report through theabove described processes.

FIG. 4 is a signal flow diagram of case 1 of FIGS. 2A and 2B accordingto an embodiment of the present disclosure. Case 1 corresponds to thecase in which an MS receives a beacon from a target BS that supports aplurality of service coverage areas, a handover condition is satisfied,and a handover is executed. Here, it is assumed that the handovercondition is set to be the case in which the beacon of the servicecoverage area that the MS receives provides the service with the QoSused by the MS, as shown in operation 206 of FIGS. 2A and 2B.

Referring to FIG. 4, in operations 410 a through 410 b, a serving BS 402transfers, to an MS 400, packet data obtained from a Serving Gate Way(S-GW) 406. Subsequently, in operation 412, the serving BS 402transmits, to the MS 400, a measurement report request at predeterminedperiods.

In this example, it is assumed that the MS 400 moves to the servicecoverage area of a target BS 404 from the service coverage area of theserving BS 402. For ease of description, it is assumed that the targetBS 404 is the small BS 110 in the millimeter wave communication systemof FIG. 1. The small BS 110 broadcasts different beacons respectivelycorresponding to the internal service coverage area 115 and the externalservice coverage area 120, as illustrated in FIG. 1. The MS 400 may ormay not receive corresponding beacons, depending on a current location.For example, it is assumed that the MS 400 is located in the externalservice coverage area of the target BS 404. Accordingly, the MS 400receives an external service coverage area beacon broadcasted by thetarget BS 404 in operation 414 a, whereas the MS 400 fails to receive aninternal service coverage area beacon transmitted by the target BS inoperation 414 b. Therefore, the MS 400 generates a measurement reportassociated with the received external service coverage area beacon andtransmits the measurement report to the serving BS 402, in operation416.

Then, the serving BS 420 determines, based on the measurement reportreceived from the MS 400, whether a handover condition is satisfied, anddetermines whether to execute a handover, in operation 418. In thisexample, it is assumed that the handover condition is set to be the casein which the external service coverage area beacon supports the QoS usedby the MS 400. FIG. 4 assumes that the small base station 110 of FIG. 1is the target BS 404 and thus, the serving BS 402 determines that ahandover with the target BS 404 which has a different RAT from theserving BS 402, that is, a handover with the target BS 404 whichcorresponds to a wireless LAN BS, requires switching an RAT. As anotherexample, when a beacon that the MS 400 receives as a target of themeasurement report corresponds to one of the beacons that respectivelycorrespond to a plurality of frequency bands supported by a singlecommunication system, the serving BS 420 determines whether to change aserving frequency band to a frequency band corresponding to the beaconthrough resource allocation. The serving BS 402 executes a preparationprocess for a handover with the target BS 404 in operation 420, andtransfers, to the MS 400, a handover command to handover to the targetBS 404, in operation 422. Accordingly, the connection between the MS 400and the target BS 404 is set up in operation 423. In operation 424 a,the target BS 404 transmits, to the S-GW 406, a path switching requestfor requesting switching of a path of packet data of the MS 400 that hasbeen transferred to the serving BS 402, to the target BS 404. Then, inresponse to the path switching request, the S-GW 406 transfers a pathswitching response to the target BS 404 in operation 424 b, the packetdata of the MS 400 is transferred to the MS 400 through the target BS404 in operations 426 a through 426 b.

Subsequently, it is assumed that the MS 400 receives the internalservice coverage area beacon of the target BS 404 in operation 428, dueto the movement of the MS 400. In operation 430, the MS 400 transfers,to the target BS 404, a measurement report associated with the internalservice coverage area beacon. In operation 432, the target BS 404recognizes that the MS 400 enters into the internal service coveragearea of the target BS 404, and executes scheduling for providing aservice through the internal service coverage area. In operation 434,the target BS 404 transfers, to the MS 400, resource allocationinformation obtained through scheduling.

FIGS. 5A and 5B are examples of a signal flow diagram of case 2 of FIGS.2A and 2B according to an embodiment of the present disclosure. Case 2according to an embodiment of the present disclosure corresponds to thecase in which an MS receives a beacon from a target BS that supports aplurality of service coverage areas, a handover condition is notsatisfied, and DC with the target BS is set up. Here, it is assumed thatthe handover condition is set to be identical to the handover conditionof operation 206 of FIGS. 2A and 2B. The DC is defined to be identicalto the DC of FIGS. 2A and 2B and thus, detailed descriptions thereofwill be omitted to avoid duplicate descriptions. FIGS. 5A and 5Bexemplify the case in which a single target BS that supports a pluralityof service coverage areas is used.

Referring to FIG. 5A, in operations 510 a through 510 b, a serving BS502 transmits and receives packet data between an S-GW 506 and an MS500. Subsequently, in operation 512, the serving BS 502 transmits, tothe MS 500, a measurement report request, at predetermined periods.

In the same manner as FIG. 1, it is assumed that the MS 500 moves to theservice coverage area of a target BS 504 from the service coverage areaof the serving BS 502. For ease of description, it is assumed that thetarget BS 504 is the small BS 110 in the millimeter wave communicationsystem of FIG. 1. The small BS 110 broadcasts different beaconsrespectively corresponding to the internal service coverage area 115 andthe external service coverage area 120, as illustrated in FIG. 1. The MS500 may or may not transmit corresponding beacons, depending on acurrent location. For example, it is assumed that the MS 500 is locatedin the external service coverage area of the target BS 504. Accordingly,the MS 500 receives an external service coverage area beacon broadcastedby the target BS 504 in operation 514 a, whereas the MS 500 fails toreceive an internal service coverage area beacon transmitted by thetarget BS 504 in operation 514 b. Therefore, the MS 500 generates only ameasurement report associated with the received external servicecoverage area beacon and transmits the measurement report to the servingBS 502, in operation 516.

Then, the serving BS 502 determines, based on the measurement reportreceived from the MS 500, whether to set up the DC with respect to theMS 500, in operation 518. In this example, it is assumed that it isdetermined to set up the DC with respect to the MS with the target BS504, since it is recognized, based on the measurement report, that thebeacon transmitted by the target BS 504 does not support the QoS used bythe MS but the target BS supports another service coverage area thatsupports the QoS. Then, the serving BS 502 communicates information onresource allocation for communication for each of the serving BS 502 andthe target BS 504. For example, the resource allocation may use a schemethat distinguishes the communication of the serving BS 502 and thecommunication of the target BS 504 through a time division scheme, ascheme of simultaneously executing the communication of the serving BS502 and the communication of the target BS 504 based on differentfrequency bands or a radio frequency (RF) chain characteristic of aterminal, or the like. The serving BS 502 transmits, to the target BS504, a DC connection request including information resource allocationinformation for the DC in operation 520 a, and receives, from the targetBS 504, a DC connection response in response to the DC connectionrequest, in operation 520 b. Subsequently, the serving BS 502 transmits,to the target BS 504, DC setup Ack indicating the reception of the DCconnection response, in operation 520 c. In operation 522, the servingBS 502 transfers, to the MS 500, resource allocation information for theDC. Through the above process, the MS 500 is in the state of having theDC set with the serving BS 502 and the target BS 504. Accordingly, whenit is assumed that a period of a subsequent measurement report has come,the MS 500 transmits a measurement report to the serving BS 502 inoperation 524 a. In operation 524 b, the MS 500 also transmits themeasurement report to the target BS. Here, it is assumed that themeasurement reports transmitted in operations 524 a and 524 b areidentical, and the format determined in the resource allocation processfor the DC is applied.

In operation 526, the serving BS 502 adjusts the current length of theperiod for the measurement report of the MS 500 based on the informationobtained from the measurement report, and determines whether to copydata to be transferred to the target BS, or the like. In particular, asdescribed in operation 214 of FIGS. 2A and 2B, when the strength of abeacon that the MS 500 receives is greater than or equal to the firstthreshold value, the current length is set to a minimum value, andreal-time data to be transferred to the MS 500 is copied. When thestrength of the beacon that the MS 500 receives is greater than or equalto the first threshold value and a difference between the signalstrength of a beacon received in a previous period, and the signalstrength of the beacon received in the current period is greater than orequal to a predetermined offset, the current length is set to be 1 stageshorter than the current length. When the difference is less than theoffset, the current length may be set to be 1 stage longer than thecurrent length.

Subsequently, referring to FIG. 5B, when a period corresponding to theadjusted current length has come, the serving BS 502 transfers ameasurement report request to the MS 500 in operation 528 a, andsimultaneously, copies and transfers, to the target BS 504, real-timedata to be transferred to the MS 500, in operation 528 b.

Subsequently, in operations 530 a and 530 b, the MS 500 transfers ameasurement report corresponding to a measurement report request ofoperation 528 a to the serving BS 502 and the target BS 504,respectively.

It is assumed that the MS 500 continuously moves and enters into theinternal service coverage area of the target BS 504. Accordingly, inoperation 532, the MS 500 receives an internal service coverage areabeacon broadcasted by the target BS 504. It is assumed that the internalservice coverage area supports the QoS used by the MS 500. In operations534 a and 534 b, the serving BS 502 transfers a measurement reportassociated with the internal service coverage area beacon to the servingBS 502 and the target BS 502, respectively. However, when it is assumedthat the current location of the MS 500 is out of the service coveragearea of the serving BS 502, the measurement report transmitted by the MS500 in operation 534 a may not be transferred to the serving BS 502.

Subsequently, in operation 536, the target BS 504 determines whether toremove the DC with the MS 500, based on the measurement report. That is,when the signal strength of a beacon obtained through the measurementreport is less than the second threshold value, or when it is determinedthat the MS 500 is disconnected from the serving BS 502, removal of theDC is determined. In operation 538, the target BS 504 transfer, to theMS 500, resource allocation information including DC informationinstructing the MS 500 to receive packet data through only the target BS504 due to the removal of the DC. Then, in operation 540, a handover iscompleted, and the MS 500 and the target BS 504 are available tocommunicate through the resource allocation information. The target BS504 transfers, to the serving BS 502, a DC removal request for removingthe DC set with the MS 500 in operation 542 a, and receives a DC removalresponse from the target BS 504 in response to the DC removal request inoperation 542 b. In operation 542 c, the target BS 504 transfers DCremoval Ack in response to the reception of the DC removal response. Inoperation 544 a, the target BS 504 transfers, to the S-GW 506, a pathswitching request for requesting switching of a path associated with theMS 500 from the serving BS 502 to the target BS 504. In operation 544 b,the target BS 504 receives a path switching response through the S-GW506, in response to the path switching request. In operation 546, thetarget BS 504 transfers, to the MS 500, resource allocation informationobtained through the packet switching response. Subsequently, the targetBS 504 transmits and receives the packet data to/from the MS 500 and theS-GW 506 using the resource allocation information through operations548 through 550.

FIG. 6 is another example of a signal flow diagram of case 2 of FIGS. 2Aand 2B according to an embodiment of the present disclosure. Case 2according to an embodiment of the present disclosure corresponds to thecase in which an MS receives a beacon from a target BS that supports aplurality of service coverage areas, a handover condition is notsatisfied, and DC with a target BS is set up. Here, the handovercondition is set to be identical to the handover condition of operation206 of FIGS. 2A and 2B. The DC is defined to be identical to the DC ofFIGS. 2A and 2B and thus, detailed descriptions thereof will be omittedto avoid duplicate descriptions. The embodiment of FIG. 6 exemplifiesthe case in which two target BSs that support a plurality of servicecoverage areas are used. Although, for ease of description, the presentspecifications exemplifies the case in which one or two target BSs thatsupport a plurality of service coverage areas are used, the presentdisclosure may be applied to the case in which a plurality of target BSsare used.

Referring to FIG. 6, in operations 610 a through 610 b, a serving BS 602transmits and receives packet data between an S-GW 608 and an MS 600.Subsequently, in operation 612, the serving BS 602 transmits, to the MS600, a measurement report request at predetermined periods.

In the same manner as FIGS. 5A and 5B, it is assumed that the MS 600moves to the service coverage areas of a target BS1 604 and a target BS2606 from the service coverage area of the serving BS 602. It is assumedthat each of the target BS1 604 and the target BS2 606 broadcastsdifferent beacons respectively corresponding to an internal servicecoverage area and an external service coverage area, in the same manneras the small BS 110 as shown in FIG. 1. The MS 600 may or may nottransmit corresponding beacons, depending on a current location. Forexample, it is assumed that the MS 600 is located in the externalservice coverage area of the target BS1 604 and the external servicecoverage area of the target BS2 606. In this example, the externalservice coverage areas of the target BS1 604 and the target BS2 606 maybe configured to partially overlap, or configured to be included in oneanother.

Accordingly, it is assumed that the MS 600 receives an external servicecoverage area beacon broadcasted by the target BS1 604 in operation 614a, and the MS 600 receives an external service coverage area beaconbroadcasted by the target BS2 606 in operation 614 b. Then, the MS 600generates a measurement report associated with each external servicecoverage area beacon of the target BS1 604 and the target BS2 606, andtransmits the generated measurement reports to the serving BS 602, inoperation 616.

Then, the serving BS 602 determines, based on the measurement reportreceived from the MS 600, whether to set up the DC with respect to theMS 600, in operation 618. In this example, it is assumed that theserving BS 602 recognizes, based on the measurement reports, that the MS600 receives beacons of at least two target BSs that support a pluralityof service coverage areas, and determines that the signal strengths ofthe beacons are greater than or equal to a handover reference thresholdvalue. The serving BS 602 determines to set up DC with respect to the MS600, with each of the target BS1 604 and the target BS2 606. The servingBS 602 generates a list of target BSs for which DC is set up(hereinafter referred to as a ‘DC setup BS list’), including the targetBS1 604 and the target BS2 606. Through operations 620 a through 620 b,DC with each of the target BS1 604 and the target BS2 606 is set up. Inthis example, the DC setup process includes a process of transferringthe DC setup BS list to a corresponding target BS. In addition, the DCsetup process may also include a process of communicating information onresource allocation for communication with each of the target BS1 604and the target BS2 606. Examples of the communication have been providedin the descriptions associated with FIGS. 5A and 5B, detaileddescriptions thereof will be omitted to avoid duplicate descriptions. Inoperation 622, the serving BS 602 transfers, to the MS 600, resourceallocation information for the DC of the DC setup process. Through theabove process, the MS 600 is in the state of having the DC set with theserving BS 602 and the target BS1 604, and having the DC set with theserving BS 602 and the target BS 2 606. Accordingly, when it is assumedthat the subsequent period of a measurement report has come, the MS 600transmits a measurement report to the serving BS 602 and each of thetarget BS1 604 and the target BS2 606, in operations 624 a through 624c. Here, it is assumed that the measurement reports transmitted inoperations 624 a and 624 b are identical, and the format determined inthe resource allocation process for the DC is applied. Subsequently,each of the serving BS 602, the target BS1 604, and the target BS2 606determines whether to remove the DC with respect to the MS 600, throughthe measurement reports received from the MS 600, in operations 626 athrough 626 c. A corresponding BS that determines removal of the DCinforms all of the BSs having the DC with the MS 600 of the removal ofthe DC of itself. For example, it is assumed that the serving BS 602recognizes, from the information obtained from the measurement report,that the target BS1 604 and the target BS2 606 simultaneously satisfythe handover condition of the MS 600. In operation 628 a, the serving BS602 executes a DC removal process for removing the DC with respect tothe MS 600 with the target BS1 604 and the target BS2 606. Although notillustrated, in the DC removal process, the serving BS 602 transmits aDC removal message to each of the target BS1 604 and the target BS2 606.Each of the target BS1 604 and the target BS2 606 transmits additionalinformation to the serving BS 602. Here, the additional informationcorresponds to load information of a corresponding BS, a signal strengthwith respect to the MS 600, and the like. When the additionalinformation is the load information, the serving BS 602 determines to bea final target for the removal of DC, a BS having the lowest load basedon load information of the target BS1 604 and the target BS2 606. In thesame manner, when the additional information is the signal strength, theserving BS 602 determines a BS having the highest signal strength amongthe target BS1 604 and the target BS2 606 to be a final target for theremoval of DC. It is assumed that the serving BS 602 determines toremove the DC with the target BS2 606 when the load or the signalstrength of the target BS2 606 is lower or higher than the load or thesignal strength of the target BS1 604, and executes the removal of theDC. Although not illustrated, the target BS2 602 of which the DC isremoved reports the removal of the DC of itself to the target BS1 604and the serving BS 602 that is associated with the DC of the MS 600. Inoperation 628 b, the serving BS 602 informs the MS 600 of the removal ofthe DC with the target BS2 606.

Then, the MS 600 is in the state of having the DC set with only thetarget BS1 604. Accordingly, in operations 630 a through 630 b, the MS600 transfers a measurement report to each of the serving BS 602 and thetarget BS1 604.

Here, it is exemplified that a serving BS determines the removal of DCwhen the DC is set up through a plurality of BSs. However, all of thetarget BSs for which the DC is set up receive measurement reports froman MS and thus, they may determine removal of DC of themselves throughthe measurement reports.

FIG. 7 is an example of a block diagram of a serving BS and a target BSaccording to an embodiment of the present disclosure.

Referring to FIG. 7, each of a serving BS and a target BS 700 includes acontroller 702, a transceiving unit 704, a handover conditiondetermining unit 706, a DC setup unit 708, and a measurement reportperiod adjusting unit 710. The configuration of a BS in FIG. 7 isseparately illustrated for each operation according to an embodiment ofthe present disclosure, and may be configured differently based on theintention of a provider or the situation.

First, when the configuration of FIG. 7 operates as a serving BS, thecontroller 701 waits for reception of a measurement report of an MS inassociation with a beacon that supports a plurality of service coverageareas through the transceiving unit 704. When it is recognized that themeasurement report is received, the controller 704 controls the handovercondition determining unit 706 to determine whether the handovercondition is satisfied based on the measurement report. Accordingly, thehandover condition determining unit 706 compares the signal strength ofthe beacon with a handover reference threshold value, and determineswhether a target BS that transmits the beacon supports the QoS used bythe MS. When the signal strength of the beacon is greater than or equalto the handover reference threshold value and the QoS used by the MS issupported, it is determined that the handover condition is satisfied.Then, the controller 702 determines to execute the handover of the MSwith the target base station.

Also, although the handover condition with respect to the MS is notsatisfied, the controller 702 determines that the QoS may be providedwhen the MS arrives at another service coverage area of the serving BSof the communication system. Accordingly, the controller 702 determinesthat the handover condition is not satisfied and determines to set upthe DC. A process of communicating information for the DC is executed.The communication includes a format associated with a measurement reportof an MS which is transmitted after the DC is set up, and resourceallocation for communication between a target BS and the MS, andcommunication between a serving BS and the MS. Detailed examples thereofhave been provided earlier and thus, detailed descriptions thereof willbe omitted to avoid duplicate descriptions.

When the signal strength of the beacon is greater than or equal to thehandover reference threshold value, the DC setup unit 708 informs thecontroller 702 of the same, and determines to remove the DC. Thecontroller 702 hands over the MS to the target base station, and removesthe DC with the target BS.

After setup of the DC as per the instruction from the controller 702,the measurement report period adjusting unit 710 compares the signalstrength of the beacon obtained from a measurement report receivedthrough the transceiving unit 704 with a first threshold value. When acomparison result shows that the signal strength of the beacon isgreater than the first threshold value, the measurement report periodadjusting unit 710 sets the current length of the measurement report toa minimum value. The controller 702 transmits a measurement reportrequest to the MS at periods corresponding to the minimum value. Whenthe signal strength of the beacon is greater than or equal to the firstthreshold value and the difference between the signal strength of apreviously received beacon and the signal strength of the beacon isgreater than or equal to a predetermined offset, the controller 702 setsthe current length to be 1 stage shorter than the current length. Also,when the difference is less than the offset, the current length may beset to be 1 stage longer than the current length. When it is determinedthat the difference is less than the offset, or the signal strength ofthe beacon is less than a second threshold value, the controller 702remove the DC.

In the same manner, when the configuration of FIG. 7 operates as atarget BS, in the state of having the DC with respect to the MS, thetransceiving unit 704 simultaneously receives data transmitted to the MSin real time through the serving BS. The handover condition determiningunit 706, the DC setup unit 708, and the measurement report periodadjusting unit 710 operate similarly to the operations of the serving BSand thus, detailed descriptions thereof will be omitted to avoidduplicate descriptions.

FIGS. 8A and 8B are examples of a signal flow diagram of DC according toan embodiment of the present disclosure.

Referring to FIGS. 8A and 8B, it is assumed that, for example, a targetBS 804 is a BS integrated with a wireless LAN and a cellular BS.Accordingly, the target BS 804 includes a wireless module and a cellularmodule corresponding to service coverage areas that support differentQoSs, and an MS 800 also includes a wireless LAN module and a cellularmodule. It is assumed that the QoS used by the MS 800 corresponds to aQoS supported by a service coverage area of a cellular module.

Referring to FIG. 8A, currently, the MS 800 transmits and receivespacket data among the MS 800, a serving BS 802, and an S-GW 806, throughthe communication state with the serving BS 802, that is, in operations810 a through 810 b. In operation 812, after receiving a measurementreport request from the serving BS 802, the MS 800 receives a beacon ofthe wireless LAN module and broadcasting information of the cellularmodule transmitted from the integrated BS 804, in operations 814 athrough 814 b. In this example, it is assumed that the broadcastinginformation of the cellular module is not received due to the locationof the MS 800.

Then, the MS 800 recognizes reception of the beacon through its wirelessLAN module, and transfers an interface message indicating the receptionof the beacon to the cellular module in operation 816. The interfacemessage is defined to be a message for interfacing between modules inthe MS 800, that is, the wireless LAN module and the cellular module. Inoperation 818, the cellular module of the MS 800 generates a measurementreport associated with the reception of the beacon and transmits themeasurement report to the serving BS 802.

It is assumed that the serving BS 802 recognizes, based on themeasurement report, that the beacon does not support the QoS of the MSbut the integrated BS supports cellular communication that supports theQoS, and determines to set up DC with the integrated BS 804, inoperation 820. In operation 822 a, the serving BS 802 transfers a DCsetup request to the integrated BS 804, and receives a DC setup responsefrom the integrated BS 804 in operation 822 b. In operation 822 c, theserving BS 802 transfers, to the integrated BS 804, a DC Ack withrespect to the reception of the DC setup response. In operations 822 athrough 822 c, a process of communicating information for DC isexecuted, and this has been described earlier and thus, detaileddescriptions thereof will be omitted to avoid duplicate descriptions. Inoperation 824, the serving BS 802 transfers, to the MS 800, resourceallocation information including communicated DC information. Inoperation 826, the cellular module of the MS 800 transfers the resourceallocation information to the wireless LAN module. In operation 828, thewireless LAN module of the MS 800 informs the wireless LAN module of theintegrated BS 804 of the reception of the resource allocationinformation.

After the DC with respect to the MS 800 is set up, in operations 830 athrough 830 b, the MS receives a beacon and broadcasting information ofeach of the wireless LAN module and the cellular module of theintegrated BS 804. In this example, it is assumed that the MS 800 hasmoved to a location where the MS 800 is able to receive both the beaconand the broadcasting information. In this example, in operation 832 thecellular module of the MS 800 transfers a measurement report to theserving BS 802, and in operation 833, the cellular module of the MS 800transfers the received broadcasting information to its wireless LANmodule through an interface message. In operation 834 b, the wirelessLAN module of the MS 800 informs the wireless LAN module of theintegrated BS 804 of the reception of the broadcasting information. Inoperation 834 c, the wireless LAN module 804 transfers the notificationto its cellular module through an interface message. Alternatively, inoperation 836, the wireless LAN module of the MS 800 transfers thenotification to the cellular module of the integrated BS 804, through acellular radio interface using random access and the like.

Subsequently, in operation 838, the integrated BS 804 recognizes thatthe MS 800 is capable of receiving its broadcasting information anddetermines to remove the DC. In operation 840, the integrated BS 804transmits, to the MS 800, resource allocation information including DCinformation instructing removal of the DC. When packet data receivedfrom the serving BS 802 through the DC state exists, the integrated BS804 transmits and receives the packet data to/from the MS 800 inoperation 842.

In operations 844 a through 844 c, the integrated BS 804 executes aprocess for removing the DC, and the corresponding process has beendescribed earlier and thus, detailed descriptions thereof will beomitted to avoid duplicate descriptions. The integrated BS 804transfers, to the S-GW 806, a path switching request for switching apath of packet data of the MS 800 from the serving BS 802 to theintegrated BS 804, in operation 846 a, and receives a path switchingresponse in response to the request, in operation 846 b. In operation848, the integrated BS 804 transmits, to the MS 800, resource allocationinformation for packet data communication with the BS 804. Subsequently,based on the resource allocation information, in operations 850 athrough 850 b, the cellular module of the MS 800, the cellular module ofthe integrated BS 804, and the S-GW transmit packet data.

FIG. 9 illustrates an example of a flowchart of operations of an MSaccording to an embodiment of the present disclosure.

Referring to FIG. 9, in operation 900, an MS generates a measurementreport as per a measurement report request of a serving BS, andtransmits the measurement report to the serving BS. In this example,according to an embodiment of the present disclosure, when themeasurement report is beacon-related information associated with abeacon that supports a plurality of service coverage areas, the servingBS determines whether a handover condition is satisfied based on thebeacon-related information. The handover condition has been describedearlier and thus, detailed descriptions thereof will be omitted to avoidduplicate descriptions. It is assumed that the determination shows thatthe MS is unable to receive the QoS used by the MS in the currentlocation, but the MS may be provided the QoS through another servicecoverage area of a target BS that transmits the beacon. The serving BSsets up the DC with respect to the MS with the target BS, copiesreal-time data to be transmitted to the MS, and simultaneously transmitsthe real-time data to the target BS. The serving BS has communicatedinformation for the DC with the target BS, which has been describedearlier and thus, detailed descriptions thereof will be omitted to avoidduplicate descriptions.

Subsequently, in operation 905, the MS determines whether informationassociated with DC is received from the serving BS. In this example, theDC-related information includes a format of a measurement report, to betransmitted to the serving BS and the target BS after the DC is set up,or resource-related information. When the determination shows that theDC-related information is not received, the MS continuously waits untilit is received.

When the determination shows that the DC-related information isreceived, the MS transmits in operation 910, to each BS that has DC setwith the serving BS, a measurement report based on a period andresources corresponding to the DC-related information.

FIG. 10 illustrates an example of a block diagram of an MS according toan embodiment of the present disclosure.

Referring to FIG. 10, an MS 1000 includes a controller 1005, a receivingunit 1010, a DC-related information determining unit 1015, and atransmitting unit 1020. The configuration of an MS in FIGS. 8A and 8Bare separately illustrated for each operation according to an embodimentof the present disclosure, and may be configured differently based onthe intention of a provider or the situation.

The receiving unit 1010 receives a measurement report, packet data, andDC-related information, from a serving BS. When the controller 1005recognizes reception of the DC-related information, the DC-relatedinformation determining unit 1015 determines a target BS for which theDC is set, resources to be allocated, a format of a measurement reporttransmitted after the DC is set up, or the like. The controller 1005controls the transmitting unit 1020 to transmit a measurement report tothe target BS and the serving BS, for which the DC is set up after theDC is set up based on the determined information.

That is, all configurations or steps of the operations illustrated inFIGS. 1 to 10 should not be interpreted as essentially structuralelements for carrying out the present disclosure, and variations andmodifications of the present disclosure may be implemented withoutdeparting from the scope of the present disclosure.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A handover method of a serving base station in acommunication system, the method comprising: if it is recognized that aterminal receives a beacon including a plurality of pieces of servicecoverage area information, determining setup of dual connectivity (DC)with respect to the terminal with a target base station that transmitsthe beacon; and if the DC is set up, determining whether to execute ahandover to the target base station based on a measurement report of theterminal which is received after the DC is set up.
 2. The method ofclaim 1, wherein the determining of the setup of the DC comprises: if afirst service coverage area that provides a service quality used by theterminal exists among a plurality of service coverage areas provided bythe target base station through the beacon, and the first coverage areais not a service coverage area corresponding to the beacon, determiningthe setup of the DC.
 3. The method of claim 1, wherein the beaconcorresponds to a service coverage area having the largest servicecoverage area, among beacons respectively corresponding to a pluralityof service coverage areas broadcasted by the target base station, andincludes information corresponding to each of the plurality of servicecoverage areas.
 4. The method of claim 1, wherein the determining ofwhether to execute the handover comprises: if a service coverage areacorresponding to a beacon obtained from the measurement report providesa service quality used by the terminal, and a signal strength of thebeacon is greater than or equal to a minimum threshold value forproviding a service to the terminal, executing the handover to thetarget base station, and removing the DC.
 5. The method of claim 4,wherein the determining of whether to execute the handover comprises: ifthe service coverage area corresponding to the beacon obtained from themeasurement report does not provide the service quality and the signalstrength of the beacon obtained from the measurement report is less thana first threshold value, and greater than or equal to a second thresholdvalue, adjusting a period of the measurement report.
 6. The method ofclaim 5, wherein the adjusting of the period comprises: if the signalstrength of the beacon obtained from the measurement report is greaterthan or equal to the first threshold value, setting a current length ofthe period to a minimum value, and transmitting, to the target basestation, real-time data to be transmitted to the terminal.
 7. The methodof claim 5, wherein the adjusting of the period comprises: if the signalstrength of the beacon obtained from the measurement report has a valuethat is at least a predetermined offset greater than a signal strengthof a previously received beacon, decreasing the current length of theperiod by a predetermined unit; and if the signal strength of the beaconobtained from the measurement report has a value that is at least thepredetermined offset less than the signal strength of the previouslyreceived beacon, increasing the current length by the predeterminedunit.
 8. The method of claim 4, wherein the determining of whether toexecute the handover comprises: if the signal strength of the beaconobtained from the measurement report is less than the second thresholdvalue, removing the DC with the target base station.
 9. A handovermethod of a target base station in a communication system, the methodcomprising: in a state where the target base station that supports aplurality of service coverage areas has dual connectivity (DC) set witha serving base station of a terminal and the terminal, receiving, fromthe terminal, a measurement report associated with a beacon of thetarget base station; and determining whether to execute a handover ofthe terminal based on the measurement report.
 10. The method of claim 9,wherein the DC is set up by the serving base station if a servicecoverage area that provides a service quality used by the terminalexists among the plurality of service coverage areas provided by thetarget base station through the beacon and the first service coveragearea is not a service coverage area corresponding to the beacon.
 11. Themethod of claim 9, wherein the beacon corresponds to a service coveragearea having the largest service coverage area, among beaconsrespectively corresponding to the plurality of service coverage areasbroadcasted by the target base station, and includes informationcorresponding to each of the plurality of service coverage areas. 12.The method of claim 9, wherein the determining of whether to execute thehandover comprises: if a service coverage area corresponding to thebeacon obtained from the measurement report provides a service qualityused by the terminal, and the signal strength of the beacon is greaterthan or equal to a minimum threshold value for providing a service tothe terminal, executing the handover of the terminal, and removing theDC.
 13. The method of claim 12, wherein the determining of whether toexecute the handover comprises: if the service coverage areacorresponding to the beacon obtained from the measurement report doesnot provide the service quality, and the signal strength of the beaconobtained from the measurement report is less than a first thresholdvalue and greater than or equal to a second threshold value, adjusting aperiod of the measurement report.
 14. The method of claim 13, whereinthe adjusting of the period of the measurement report comprises: if thesignal strength of the beacon obtained from the measurement report isgreater than or equal to the first threshold value, setting a currentlength of the period to a minimum value, and transmitting, to the targetbase station, real-time data to be transmitted to the terminal.
 15. Themethod of claim 13, wherein the adjusting of the period of themeasurement report comprises: if the signal strength of the beaconobtained from the measurement report has a value that is at least apredetermined offset greater than a signal strength of a previouslyreceived beacon, decreasing a current length of the period by apredetermined unit; and if the signal strength of the beacon obtainedfrom the measurement report has a value that is at least thepredetermined offset less than the signal strength of the previouslyreceived beacon, increasing the current length of the period by thepredetermined unit.
 16. The method of claim 12, wherein, if the signalstrength of the beacon obtained from the measurement report is less thanthe second threshold value, removing the DC of the target base station.17. A handover method of a terminal in a communication system, themethod comprising: if a beacon transmitted by a target base station thatprovides a plurality of service coverage areas is received, transmittingbeacon-related information to a serving base station; receiving, fromthe serving base station, information for dual connectivity (DC) withthe target base station; and transmitting a measurement reportcorresponding to a coming period to the serving base station and thetarget base station, based on the information for the DC.
 18. The methodof claim 17, wherein the DC is set up by the serving base station if afirst service coverage area that provides a service quality used by theterminal exists among the plurality of service coverage areas and thefirst service coverage area is not a service coverage area correspondingto the beacon.
 19. The method of claim 17, wherein the beaconcorresponds to a service coverage area having the largest servicecoverage area, among beacons respectively corresponding to the pluralityof service coverage areas broadcasted by the target base station, andincludes information corresponding to each of the plurality of servicecoverage areas.
 20. A serving base station that executes a handover in acommunication system, the serving base station comprises: a controllerconfigured to determine setup of dual connectivity (DC) with a targetbase station that transmits a beacon to a terminal if it is recognizedthat the terminal receives the beacon including a plurality of pieces ofservice coverage area information, and if the DC is set up, to determinewhether to execute a handover to the target base station based on ameasurement report of the terminal which is received after the DC is setup.
 21. The serving base station of claim 20, wherein the controller isconfigured to determine the setup of the DC if a first service coveragearea that provides a service quality used by the terminal exists among aplurality of service coverage areas provided by the target base stationthrough the beacon, and the first service coverage area is not a servicecoverage area corresponding to the beacon.
 22. The serving base stationof claim 20, wherein the beacon corresponds to a service coverage areahaving the largest service coverage area, among beacons respectivelycorresponding to a plurality of service coverage areas broadcasted bythe target base station, and includes information corresponding to eachof the plurality of service coverage areas.
 23. The serving base stationof claim 20, wherein the controller is configured to execute thehandover to the target base station and removes the DC if a servicecoverage area corresponding to a beacon obtained from the measurementreport provides a service quality used by the terminal, and a signalstrength of the beacon is greater than or equal to a minimum thresholdvalue for providing a service to the terminal.
 24. The serving basestation of claim 23, wherein the controller is configured to adjust aperiod of the measurement report if the service coverage areacorresponding to the beacon obtained from the measurement report doesnot provide the service quality and the signal strength of the beaconobtained from the measurement report is less than a first thresholdvalue and greater than or equal to a second threshold value.
 25. Theserving base station of claim 24, wherein the controller is configuredto control the current length by setting a current length of the periodto a minimum value, and to control a transceiving unit to transmit, tothe target base station, real-time data to be transmitted to theterminal if the signal strength of the beacon obtained from themeasurement report is greater than or equal to the first thresholdvalue.
 26. The serving base station of claim 24, wherein the controlleris configured to decrease the current length of the period by apredetermined unit if the signal strength of the beacon obtained fromthe measurement report has a value that is at least a predeterminedoffset greater than a signal strength of a previously received beacon,and wherein the controller is configured to increase the current lengthby the predetermined unit if the signal strength of the beacon obtainedfrom the measurement report has a value that is at least the offset lessthan the signal strength of the previously received beacon.
 27. Theserving base station of claim 23, wherein the controller is configuredto remove the DC with the target base station if the signal strength ofthe beacon obtained from the measurement report is less than the secondthreshold value.
 28. A target base station that executes a handover in acommunication system, the target base station comprising: a receivingunit configured to receive, from a terminal, a measurement reportassociated with a beacon of the target base station in a state where thetarget base station that supports a plurality of service coverage areashas dual connectivity (DC) set with a serving base station of theterminal and the terminal; and a controller configured to determinewhether to execute a handover of the terminal based on the measurementreport.
 29. The target base station of claim 28, wherein the DC is setup by the serving base station if a service coverage area that providesa service quality used by the terminal exists among the plurality ofservice coverage areas provided by the target base station through thebeacon and the first service coverage area is not a service coveragearea corresponding to the beacon.
 30. The target base station of claim28, wherein the beacon corresponds to a service coverage area having thelargest service coverage area, among beacons respectively correspondingto the plurality of service coverage areas broadcasted by the targetbase station, and includes information corresponding to each of theplurality of service coverage areas.
 31. The target base station ofclaim 28, wherein the controller is configured to execute the handoverof the terminal and to remove the DC if a service coverage areacorresponding to the beacon obtained from the measurement reportprovides a service quality used by the terminal.
 32. The target basestation of claim 31, wherein the controller is configured to adjust aperiod of the measurement report if the service coverage areacorresponding to the beacon obtained from the measurement report doesnot provide the service quality, and a signal strength of the beaconobtained from the measurement report is less than a first thresholdvalue and greater than or equal to a second threshold value
 33. Thetarget base station of claim 32, wherein the controller is configured toset a current length of the period to a minimum value and to transmit,to the target base station, real-time data to be transmitted theterminal if the signal strength of the beacon obtained from themeasurement report is greater than or equal to the first thresholdvalue.
 34. The target base station of claim 32, wherein the controlleris configured to decrease a current length of the period by apredetermined unit if the signal strength of the beacon obtained fromthe measurement report has a value that is at least a predeterminedoffset greater than a signal strength of a previously received beacon,and wherein the controller is configured to increase the current lengthof the period by the predetermined unit if the signal strength of thebeacon obtained from the measurement report has a value that is at leastthe predetermined offset less than the signal strength of the previouslyreceived beacon.
 35. The target base station of claim 28, wherein thecontroller is configured to remove the DC of the target base station ifthe signal strength of the beacon obtained from the measurement reportis less than the second threshold value.
 36. A terminal that executes ahandover in a communication system, the terminal comprising: acontroller configured to control a transceiving unit to transmitbeacon-related information to a serving base station if the terminalreceives a beacon transmitted by a target base station that provides aplurality of service coverage areas to receive, from the serving basestation, information for dual connectivity (DC) with the target basestation, and to transmit a measurement report corresponding to a comingperiod, to the serving base station and the target base station, basedon the information for the DC.
 37. The terminal of claim 36, wherein theDC is set up by the serving base station if a first service coveragearea that provides a service quality used by the terminal exists amongthe plurality of service coverage areas, and the first service coveragearea is not a service coverage area corresponding to the beacon.
 38. Theterminal of claim 36, wherein the beacon corresponds to a servicecoverage area having the largest service coverage area, among beaconsrespectively corresponding to the plurality of service coverage areasbroadcasted by the target base station, and includes informationcorresponding to each of the plurality of service coverage areas.